Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$169.96	5.231%	$178.8506	$178.85	$178.85	$178.90
Purchase #2	$55.86	9.523%	$61.1795	$61.18	$61.20	$61.20
Purchase #3	$17.98	3.242%	$18.5629	$18.56	$18.55	$18.60
Purchase #4	$245.77	5.148%	$258.4222	$258.42	$258.40	$258.40
Purchase #5	$30.73	8.512%	$33.3457	$33.35	$33.35	$33.30
Purchase #6	$233.70	12.169%	$262.139	$262.14	$262.15	$262.10
Purchase #7	$53.88	13.314%	$61.0536	$61.05	$61.05	$61.10
7 purchase totals =	$807.88		$873.5535	$873.55	$873.55	$873.60